In general, in the case of carrying out color reproduction with display, printer, and the like, such a method has been adopted that, based on the three-primary-color theory, an original tristimulus value and an output tristimulus value are coupled (see Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2003-333,355, and Japanese Unexamined Patent Publication (KOKAI) Gazette No. 7-50,760, for instance).
In such color reproduction, in order to identify the original tristimulus value, a color of a body is measured using a spectroscopic color-measuring method, for instance. In this spectroscopic color-measuring method, a spectrophotometer, which has a built-in specific light source for measurement and which is adapted for measuring body colors, has been used.
Specifically, in the spectroscopic color-measuring method, a light is emitted from the specific light source for measurement, which is built-in inside the spectrophotometer serving as a body-color measuring instrument, to a body, and thereby a reflectivity (spectroscopic-solid-angle reflectivity) for every wavelength of a reflected light from the body (for every spectrum thereof) is measured in a visible-light wavelength range of 400-700 nm, for instance. And, tristimulus values are found by means of such a calculation that values of the reflectivities (spectroscopic distribution) are multiplied by a color-matching function to carry out integration.
A body color can be determined depending by means of the dispersion of light source and the reflectivity of the body, that is, by means of (dispersion of light source) X (reflectivity of body).
However, a body including fluorescent material has such a property that, in the low-wavelength section of visible-light range, it is excited to increase the reflectivity by means of the ultraviolet-range energy of light source (see FIG. 8). Accordingly, in the case of exposing a body including fluorescent material to a light source, the reflectivity has changed depending on a property of the light source (ultraviolet content).
Here, there is such a case that ultraviolet is included abundantly in the light source of living room in general; on the contrary the ultraviolet content is less in the measurement light source of the above-described spectrophotometer serving as a body-color measuring instrument. Accordingly, even when measuring the reflectivity of body including fluorescent material while irradiating it with a specific light source for measurement from this spectrophotometer, the value has become different from the actual reflectivity. That is, when the light source of living room differs from the measurement light source of spectrophotometer, a color, which is different from a color of the body including fluorescent material that an observer can view actually, has come to be measured with the spectrophotometer.
For example, as illustrated in FIG. 7, in the “D65” light serving as the light source of a living room (the curve “A” in FIG. 7, that is, a tungsten light, for instance), the ultraviolet-region energy is large; on the other hand, in the “A” light serving as the measurement light source of spectrophotometer (the curve “B” in FIG. 7), the ultraviolet-region energy is small. And, as illustrated in FIG. 8, in the case of body including fluorescent material, the reflectivity of the “D65” light serving as the light source of a living room (the curve “A” in FIG. 8) is larger in the low-wavelength section of visible-light range than the reflectivity of the “A” light serving as the measurement light source of spectrophotometer therein (the curve “B” in FIG. 8).
Therefore, even when identifying a color of a body including fluorescent material using a spectrophotometer for body-color measurement that possesses a specific light source for measurement, the color of the body has become different from an actual color of the body that an observer is viewing in a living room, and thereby there has been such a problem that it is not possible to accurately measure a color of body including fluorescent material.